The present invention is directed to a method for dynamic route recommendation in an inner city region for a vehicle with a self-sufficient navigation system based on a mobile radio service and a traffic routing and information center, whereby the vehicle has a navigation and mobile radio means.
What is meant by a "dynamic" route is a time-beneficial route that takes currently existing construction sites and traffic impediments into consideration as well as the current traffic situation. The method disclosed herein is applicable to the inner city region.
A number of vehicle navigation systems have been disclosed that are essentially self-sufficient navigation systems. That is, they have a data memory, a digitized street layout map on board. All geographic data on the basis whereof the route from a current position to a desired destination can be calculated and displayed for a car driver are stored on such a mass storage. A number of proposals have already been made for making this more dynamic. A known routing and information system provides a beacon system as infrastructure via which all dynamic route information are transmitted continuously in broadcast mode. Such a navigation system is disclosed by German Letters Patent 29 23 634. The disadvantage of this system, however, is that extremely high introduction costs are needed because of the required infrastructure.
For making route recommendations dynamic, it has already been proposed to employ the radio data system, RDS/TMC. The traffic message channel (TMC), however, is only composed of a very narrow data channel, so that only traffic events on the [freeway system] can be transmitted thereover for the foreseeable time; the channel capacity is too low for inner city information.
Another proposal for making route recommendations dynamic is based on the mobile radiotelephone network within the framework of a broadcast mode. All current changes compared to the information deposited in a data storage in the vehicle are thereby transmitted via the mobile radiotelephone network, for example changing travel times or all construction sites valid at the time. The vehicle device itself can then calculate the shortest route. However, an extremely high calculating capacity is needed in the vehicle device given this method. Further, there is a synchronization problem when a central that administers the dynamic data and the vehicle devices in the individual vehicles do not start at the same initial state of the digital map.
Over and above this, a dialogue system has been proposed via a mobile radiotelephone network. The driver has no self-sufficient database on board. Instead, the currently best route is transmitted to him as needed.
German Published Application DE-OS-1 95 19 066 discloses a method wherein a vehicle transmits a start and destination position to a traffic routing central via a mobile radiotelephone network, the central calculates the currently best route management and communicates it to the vehicle via the mobile radiotelephone network. Further destination guidance ensues in the vehicle with navigation means carried along in the vehicle in the form of a digitized street map, a GPS receiver (global positioning system) and a computer, whereby data for route management modified due to a new traffic situation are communicated as needed to the vehicle via the mobile radiotelephone network.
However, these last two systems have problems in the inner city region, namely time shifts arise between traveling or leaving the recommended route and subsequent rephase-in. A certain time during which the vehicle continues to move can pass anyway between inquiry and reply from a central location. The position at the time of the inquiry thus no longer coincides with the position at the time of the reply. In an inner city network, which has very dense street patterns, the vehicle can be located on one of several outbound streets. Contact with a central location is necessary in order to obtain coordinates of a destination. This, however, is not necessarily established at every position. The driver must then wait until such contact has been made.
Numerous methods are known in the prior art for calculating a route from a starting point to a destination point. One skilled in the art would readily know how to perform such calculations from, for example, U.S. Pat. Nos. 4,962,458; 4,570,227; 4,796,189; 5,272,638; 5,502,640; and 5,023,798. These patents are hereby incorporated by reference in order to provide for calculation of a first course route recommendation from a current position to the destination, and for calculating a presumed position of the vehicle after the predetermined period of time, and for calculating a second updated route recommendation from the presumed position to the destination.